System for electrochemically processing a workpiece

ABSTRACT

A reactor for electrochemically processing at least one surface of a microelectronic workpiece is set forth. The reactor comprises a reactor head including a workpiece support that has one or more electrical contacts positioned to make electrical contact with the microelectronic workpiece. The reactor also includes a processing container having a plurality of nozzles angularly disposed in a sidewall of a principal fluid flow chamber at a level within the principal fluid flow chamber below a surface of a bath of processing fluid normally contained therein during electrochemical processing. A plurality of anodes are disposed at different elevations in the principal fluid flow chamber so as to place them at difference distances from a microelectronic workpiece under process without an intermediate diffuser between the plurality of anodes and the microelectronic workpiece under process. One or more of the plurality of anodes may be in close proximity to the workpiece under process. Still further, one or more of the plurality of anodes may be a virtual anode. The present invention also related to multi-level anode configurations within a principal fluid flow chamber and methods of using the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of prior InternationalApplication No. PCT/US00/10120, filed on Apr. 13, 2000 in the Englishlanguage and published in the English language as InternationalPublication No. WO00/61498, which in turn claims priority to thefollowing three U.S. Provisional Applications: U.S. Ser. No. 60/129,055,entitled “WORKPIECE PROCESSOR HAVING IMPROVED PROCESSING CHAMBER”, filedApr. 13, 1999; U.S. Ser. No. 60/143,769, entitled “WORKPIECE PROCESSINGHAVING IMPROVED PROCESSING CHAMBER”, filed Jul. 12, 1999, U.S. Ser. No.60/182,160 entitled “WORKPIECE PROCESSOR HAVING IMPROVED PROCESSINGCHAMBER”, filed Feb. 14, 2000. The entire disclosures of all three ofthe prior applications, as well as International Publication No.WO00/61498, are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The fabrication of microelectronic components from a microelectronicworkpiece, such as a semiconductor wafer substrate, polymer substrate,etc., involves a substantial number of processes. For purposes of thepresent application, a microelectronic workpiece is defined to include aworkpiece formed from a substrate upon which microelectronic circuits orcomponents, data storage elements or layers, and/or micro-mechanicalelements are formed. There are a number of different processingoperations performed on the microelectronic workpiece to fabricate themicroelectronic component(s). Such operations include, for example,material deposition, patterning, doping, chemical mechanical polishing,electropolishing, and heat treatment.

Material deposition processing involves depositing or otherwise formingthin layers of material on the surface of the microelectronic workpiece(hereinafter described as, but not limited to, a semiconductor wafer).Patterning provides removal of selected portions of these added layers.Doping of the semiconductor wafer, or similar microelectronic workpiece,is the process of adding impurities known as “dopants” to the selectedportions of the wafer to alter the electrical characteristics of thesubstrate material. Heat treatment of the semiconductor wafer involvesheating and/or cooling the wafer to achieve specific process results.Chemical mechanical polishing involves the removal of material through acombined chemical/mechanical process while electropolishing involves theremoval of material from a workpiece surface using electrochemicalreactions.

Numerous processing devices, known as processing “tools”, have beendeveloped to implement the foregoing processing operations. These toolstake on different configurations depending on the type of workpiece usedin the fabrication process and the process or processes executed by thetool. One tool configuration, known as the LT-210C™ processing tool andavailable from Semitool, Inc., of Kalispell, Mont., includes a pluralityof microelectronic workpiece processing stations that utilize aworkpiece holder and a process bowl or container for implementing wetprocessing operations. Such wet processing operations includeelectroplating, etching, cleaning, electroless deposition,electropolishing, etc.. In connection with the present invention, it isthe electrochemical processing stations used in the LT-210C™ that arenoteworthy. Such electrochemical processing stations perform theforegoing electroplating, electropolishing, anodization, etc., of themicroelectronic workpiece. It will be recognized that theelectrochemical processing system set forth herein is readily adapted toimplement each of the foregoing electrochemical processes.

In accordance with one configuration of the LT-210C™ tool, theelectroplating stations include a workpiece holder and a processcontainer that are disposed proximate one another. The workpiece holderand process container are operated to bring the microelectronicworkpiece held by the workpiece holder into contact with anelectroplating fluid disposed in the process container to form aprocessing chamber. Restricting the electroplating solution to theappropriate portions of the workpiece, however, is often problematic.Additionally, ensuring proper mass transfer conditions between theelectroplating solution and the surface of the workpiece can bedifficult. Absent such mass transfer control, the electrochemicalprocessing of the workpiece surface can often be non-uniform. This canbe particularly problematic in connection with the electroplating ofmetals. Still further, control of the shape and magnitude of theelectric field is increasingly important.

Conventional electrochemical reactors have utilized various techniquesto bring the electroplating solution into contact with the surface ofthe workpiece in a controlled manner. For example, the electroplatingsolution may be brought into contact with the surface of the workpieceusing partial or full immersion processing in which the electroplatingsolution resides in a processing container and at least one surface ofthe workpiece is brought into contact with or below the surface of theelectroplating solution.

Electroplating and other electrochemical processes have become importantin the production of semiconductor integrated circuits and othermicroelectronic devices from microelectronic workpieces. For example,electroplating is often used in the formation of one or more metallayers on the workpiece. These metal layers are often used toelectrically interconnect the various devices of the integrated-circuit.Further, the structures formed from the metal layers may constitutemicroelectronic devices such as read/write heads, etc.

Electroplated metals typically include copper, nickel, gold, platinum,solder, nickel-iron, etc. Electroplating is generally effected byinitial formation of a seed layer on the microelectronic workpiece inthe form of a very thin layer of metal, whereby the surface of themicroelectronic workpiece is rendered electrically conductive. Thiselectro-conductivity permits subsequent formation of a blanket orpatterned layer of the desired metal by electroplating. Subsequentprocessing, such as chemical mechanical planarization, may be used toremove unwanted portions of the patterned or metal blanket layer formedduring electroplating, resulting in the formation of the desiredmetallized structure.

Electropolishing of metals at the surface of a workpiece involves theremoval of at least some of the metal using an electrochemical process.The electrochemical process is effectively the reverse of theelectroplating reaction and is often carried out using the same orsimilar reactors as electroplating.

Existing electroplating processing containers often provide a continuousflow of electroplating solution to the electroplating chamber through asingle inlet disposed at the bottom portion of the chamber. Oneembodiment of such a processing container is illustrated in FIG. 1A. Asillustrated, the electroplating reactor, shown generally at 1, includesa electroplating processing container 2 that is used to contain a flowof electroplating solution provided through a fluid inlet 3 disposed ata lower portion of the container 2. In such a reactor, theelectroplating solution completes an electrical circuit path between ananode 4 and a surface of workpiece 5, which functions as a cathode.

The electroplating reactions that take place at the surface of themicroelectronic workpiece are dependent on species mass transport (e.g.,copper ions, platinum ions, gold ions, etc.) to the microelectronicworkpiece surface through a diffusion layer (a.k.a., mass transportlayer) that forms proximate the microelectronic workpiece's surface. Itis desirable to have a diffusion layer that is both thin and uniformover the surface of the microelectronic workpiece if a uniformelectroplated film is to be deposited within a reasonable amount oftime.

Even distribution of the electroplating solution over the workpiecesurface to control the thickness and uniformity of the diffusion layerin the processing container of FIG. 1A is facilitated, for example, by adiffuser 6 or the like that is disposed between the single inlet and theworkpiece surface. The diffuser includes a plurality of apertures 7 thatare provided to disburse the stream of electroplating fluid providedfrom the processing fluid inlet 3 as evenly as possible across thesurface of the workpiece 5.

Although substantial improvements in diffusion layer control result fromthe use of a diffuser, such control is limited. With reference to FIG.1A, localized areas 8 of increased flow velocity normal to the surfaceof the microelectronic workpiece are often generated by the diffuser 6.These localized areas generally correspond to the position of apertures7 of the diffuser 6. This effect is increased as the diffuser 6 is movedcloser to the workpiece.

The present inventors have found that these localized areas of increasedflow velocity at the surface of the workpiece affect the diffusion layerconditions and can result in non-uniform deposition of the electroplatedmaterial over the surface of the workpiece. Diffuser hole patternconfigurations also affect the distribution of the electric field sincethe diffuser is disposed between the anode and workpiece, and can resultin non-uniform deposition of the electroplated material. In the reactorillustrated in FIG. 1A, the electric field tends to be concentrated atlocalized areas 8 corresponding to the apertures in the diffuser. Theseeffects in the localized areas 8 are dependent on diffuser distance fromthe workpiece and the diffuser hole size and pattern.

Another problem often encountered in electroplating is disruption of thediffusion layer due to the entrapment and evolvement of gasses duringthe electroplating process. For example, bubbles can be created in theplumbing and pumping system of the processing equipment. Electroplatingis thus inhibited at those sites on the surface of the workpiece towhich the bubbles migrate. Gas evolvement is particularly a concern whenan inert anode is utilized since inert anodes tend to generate gasbubbles as a result of the anodic reactions that take place at theanode's surface.

Consumable anodes are often used to reduce the evolvement of gas bubblesin the electroplating solution and to maintain bath stability. However,consumable anodes frequently have a passivated film surface that must bemaintained. They also erode into the plating solution changing thedimensional tolerances. Ultimately, they must be replaced therebyincreasing the amount of maintenance required to keep the tooloperational When compared to tools using inert anodes.

Another challenge associated with the plating of uniform films is thechanging resistance of the plated film. The initial seed layer can havea high resistance and this resistance decreases as the film becomesthicker. The changing resistance makes it difficult for a given set ofchamber hardware to yield optimal uniformity on a variety of seed layersand deposited film thicknesses.

In view of the foregoing, the present inventors have developed a systemfor electrochemically processing a microelectronic workpiece that canreadily adapt to a wide range of electrochemical processing requirements(e.g., seed layer thicknesses, seed layer types, electroplatingmaterials, electrolyte bath properties, etc.). The system can adapt tosuch electrochemical processing requirements while concurrentlyproviding a controlled, substantially uniform diffusion layer at thesurface of the workpiece that assists in providing a correspondingsubstantially uniform processing of the workpiece surface (e.g., uniformdeposition of the electroplated material).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is schematic block diagram of an immersion processing reactorassembly that incorporates a diffuser to distribute a flow of processingfluid across a surface of a workpiece.

FIG. 1B is a cross-sectional view of one embodiment of a reactorassembly that may incorporate the present invention.

FIG. 2 is a schematic diagram of one embodiment of a reactor chamberthat may be used in the reactor assembly of FIG. 1B and includes anillustration of the velocity flow profiles associated with the flow ofprocessing fluid through the reactor chamber.

FIGS. 3A-5 illustrate a specific construction of a complete processingchamber assembly that has been specifically adapted for electrochemicalprocessing of a semiconductor wafer and that has been implemented toachieve the velocity flow profiles set forth in FIG. 2.

FIGS. 6 and 7 illustrate two embodiments of processing tools that mayincorporate one or more processing stations constructed in accordancewith the teachings of the present invention.

FIGS. 8 and 9 are a cross-sectional views of illustrative velocity flowcontours of the processing chamber embodiment of FIGS. 6 and 7.

FIGS. 10 and 11 are graphs illustrating the manner in which the anodeconfiguration of the processing chamber may be employed to achieveuniform plating.

FIGS. 12 and 13 illustrate a modified version of the processing chamberof FIGS. 6 and 7.

FIGS. 14 and 15 illustrate two embodiments of processing tools that mayincorporate one or more processing stations constructed in accordancewith the teachings of the present invention.

SUMMARY OF THE INVENTIONS

A reactor for electrochemically processing at least one surface of amicroelectronic workpiece is set forth. The reactor comprises a reactorhead including a workpiece support that has one or more electricalcontacts positioned to make electrical contact with the microelectronicworkpiece. The reactor also includes a processing container having aplurality of nozzles angularly disposed in a sidewall of a principalfluid flow chamber at a level within the principal fluid flow chamberbelow a surface of a bath of processing fluid normally contained thereinduring electrochemical processing. A plurality of anodes are disposed atdifferent elevations in the principal fluid flow chamber so as to placethem at different distances from a microelectronic workpiece underprocess without an intermediate diffuser between the plurality of anodesand the microelectronic workpiece under process. One or more of theplurality of anodes may be in close proximity to the workpiece underprocess. Still further, one or more of the plurality of anodes may be avirtual anode. The present invention also relates to multi-level anodeconfigurations within a principal fluid flow chamber and methods ofusing the same.

DETAILED DESCRIPTION OF THE INVENTION

Basic Reactor Components

With reference to FIG. 1B, there is shown a reactor assembly 20 forelectroplating a microelectronic workpiece 25, such as a semiconductorwafer. Generally stated, the reactor assembly 20 is comprised of areactor head 30 and a corresponding reactor base, shown generally at 37and described in substantial detail below, in which the electroplatingsolution is disposed. The reactor of FIG. 1B can also be used toimplement electrochemical processing operations other thanelectroplating (e.g., electropolishing, anodization, etc.).

The reactor head 30 of the electroplating reactor assembly may comprisedof a stationary assembly 70 and a rotor assembly 75. Rotor assembly 75is configured to receive and carry an associated microelectronicworkpiece 25, position the microelectronic workpiece in a process-sidedown orientation within a container of reactor base 37, and to rotate orspin the workpiece while joining its electrically-conductive surface inthe plating circuit of the reactor assembly 20. The rotor assembly 75includes one or more cathode contacts that provide electroplating powerto the surface of the microelectronic workpiece. In the illustratedembodiment, a cathode contact assembly is shown generally at 85 and isdescribed in further detail below. It will be recognized, however, thatbackside contact may be implemented in lieu of front side contact whenthe substrate is conductive or when an alternative electricallyconductive path is provided between the back side of the microelectronicworkpiece and the front side thereof.

The reactor head 30 is typically mounted on a lift/rotate apparatuswhich is configured to rotate the reactor head 30 from anupwardly-facing disposition in which it receives the microelectronicworkpiece to be plated, to a downwardly facing disposition in which thesurface of the microelectronic workpiece to be plated is positioned sothat it may be brought into contact with the electroplating solution inreactor base 37, either planar or at a given angle. A robotic arm, whichpreferably includes an end effector, is typically employed for placingthe microelectronic workpiece 25 in position on the rotor assembly 75,and for removing the plated microelectronic workpiece from within therotor assembly. The contact assembly 85 may be operated between an openstate that allows the microelectronic workpiece to be placed on therotor assembly 75, and a closed state that secures the microelectronicworkpiece to the rotor assembly and brings the electrically conductivecomponents of the contact assembly 85 into electrical engagement withthe surface of the microelectronic workpiece that is to be plated.

It will be recognized that other reactor assembly configurations may beused with the inventive aspects of the disclosed reactor chamber, theforegoing being merely illustrative.

Electrochemical Processing Container

FIG. 2 illustrates the basic construction of processing base 37 and acorresponding computer simulation of the flow velocity contour patternresulting from the processing container construction. As illustrated,the processing base 37 generally comprises a main fluid flow chamber505, an antechamber 510, a fluid inlet 515, a plenum 520, a flowdiffuser 525 separating the plenum 520 from the antechamber 510, and anozzle/slot assembly 530 separating the plenum 520 from the main chamber505. These components cooperate to provide a flow of electrochemicalprocessing fluid (here, of the electroplating solution) at themicroelectronic workpiece 25 that has a substantially radiallyindependent normal component. In the illustrated embodiment, theimpinging flow is centered about central axis 537 and possesses a nearlyuniform component normal to the surface of the microelectronic workpiece25. This results in a substantially uniform mass flux to themicroelectronic workpiece surface that, in turn, enables substantiallyuniform processing thereof.

Notably, as will be clear from the description below, this desirableflow characteristic is achieved without the use of a diffuser disposedbetween the anode(s) and surface of the microelectronic workpiece thatis to be electrochemically processed (e.g.. electroplated). As such, theanodes used in the electroplating reactor can be placed in closeproximity to the surface of the microelectronic workpiece to therebyprovide substantial control over local electrical field/current densityparameters used in the electroplating process. This substantial degreeof control over the electrical parameters allows the reactor to bereadily adapted to meet a wide range of electroplating requirements(e.g., seed layer thickness, seed layer type, electroplated material,electrolyte bath properties, etc.) without a corresponding change in thereactor hardware. Rather, adaptations can be implemented by altering theelectrical parameters used in the electroplating process through, forexample, software control of the power provided to the anodes.

The reactor design thus effectively de-couples the fluid flow fromadjustments to the electric field. An advantage of this approach is thata chamber with nearly ideal flow for electroplating and otherelectrochemical processes (i.e., a design which provides a substantiallyuniform diffusion layer across the microelectronic workpiece) may bedesigned that will not be degraded when electroplating or otherelectrochemical process applications require significant changes to theelectric field.

The foregoing advantages can be more greatly appreciated through acomparison with the prior art reactor design illustrated in FIG. 1A. Inthat design, the diffuser must be moved closer to the surface of theworkpiece if the distance between the anode and the workpiece surface isto be reduced. However, moving the diffuser closer to the workpiecesignificantly alters the flow characteristics of the electroplatingfluid at the surface of the workpiece. More particularly, the closeproximity between the diffuser and the surface of the workpieceintroduces a corresponding increase in the magnitude of the normalcomponents of the flow velocity at local areas 8. As such, the anodecannot be moved so that it is in close proximity to the surface of themicroelectronic workpiece that is to be electroplated withoutintroducing substantial diffusion layer control problems and undesirablelocalized increases in the electrical field corresponding to the patternof apertures in the diffuser. Since the anode cannot be moved in closeproximity to the surface of the microelectronic workpiece, theadvantages associated with increased control of the electricalcharacteristics of the electrochemical process cannot be realized. Stillfurther, movement of the diffuser to a position in close proximity withthe microelectronic workpiece effectively generates a plurality ofvirtual anodes defined by the hole pattern of the diffuser. Given theclose proximity of these virtual anodes to the microelectronic workpiecesurface, the virtual anodes have a highly localized effect. Thus highlylocalized effect cannot generally be controlled with any degree ofaccuracy given that any such control is solely effected by varying thepower to the single, real anode. A substantially uniform electroplatedfilm is thus difficult to achieve with such a plurality of looselycontrolled virtual anodes.

With reference again to FIG. 2, electroplating solution is providedthrough inlet 515 disposed at the bottom of the base 37. The fluid fromthe inlet 515 is directed therefrom at a relatively high velocitythrough antechamber 510. In the illustrated embodiment, antechamber 510includes an acceleration channel 540 through which the electroplatingsolution flows radially from the fluid inlet 515 toward fluid flowregion 545 of antechamber 510. Fluid flow region 545 has a generallyinverted U-shaped cross-section that is substantially wider at itsoutlet region proximate flow diffuser 525 than at its inlet regionproximate channel 540. This variation in the cross-section assists inremoving any gas bubbles from the electroplating solution before theelectroplating solution is allowed to enter the main chamber 505. Gasbubbles that would otherwise enter the main chamber 505 are allowed toexit the processing base 37 through a gas outlet (not illustrated inFIG. 2, but illustrated in the embodiment shown in FIGS. 3-5) disposedat an upper portion of the antechamber 510.

Electroplating solution within antechamber 510 is ultimately supplied tomain chamber 505. To this end, the electroplating solution is firstdirected to flow from a relatively high-pressure region 550 of theantechamber 510 to the comparatively lower-pressure plenum 520 throughflow diffuser 525. Nozzle assembly 530 includes a plurality of nozzlesor slots 535 that are disposed at a slight angle with respect tohorizontal. Electroplating solution exits plenum 520 through nozzles 535with fluid velocity components in the vertical and radial directions.

Main chamber 505 is defined at its upper region by a contoured sidewall560 and a slanted sidewall 565. The contoured sidewall 560 assists inpreventing fluid flow separation as the electroplating solution exitsnozzles 535 (particularly the uppermost nozzle(s)) and turns upwardtoward the surface of microelectronic workpiece 25. Beyond breakpoint570, fluid flow separation will not substantially affect the uniformityof the normal flow. As such, sidewall 565 can generally have any shape,including a continuation of the shape of contoured sidewall 560. In thespecific embodiment disclosed here, sidewall 565 is slanted and, as willbe explained in further detail below, is used to support one or moreanodes.

Electroplating solution exits from main chamber 505 through a generallyannular outlet 572. Fluid exiting outlet 572 may be provided to afurther exterior chamber for disposal or may be replenished forre-circulation through the electroplating solution supply system.

The processing base 37 is also provided with one or more anodes. In theillustrated embodiment, a principal anode 580 is disposed in the lowerportion of the main chamber 505. If the peripheral edges of the surfaceof the microelectronic workpiece 25 extend radially beyond the extent ofcontoured sidewall 560, then the peripheral edges are electricallyshielded from principal anode 580 and reduced plating will take place inthose regions. As such, a plurality of annular anodes 585 are disposedin a generally concentric manner on slanted sidewall 565 to provide aflow of electroplating current to the peripheral regions.

Anodes 580 and 585 of the illustrated embodiment are disposed atdifferent distances from the surface of the microelectronic workpiece 25that is being electroplated. More particularly, the anodes 580 and 585are concentrically disposed in different horizontal planes. Such aconcentric arrangement combined with the vertical differences allow theanodes 580 and 585 to be effectively placed close to the surface of themicroelectronic workpiece 25 without generating a corresponding adverseimpact on the flow pattern as tailored by nozzles 535.

The effect and degree of control that an anode has on the electroplatingof microelectronic workpiece 25 is dependent on the effective distancebetween that anode and the surface of the microelectronic workpiece thatis being electroplated. More particularly, all other things being equal,an anode that is effectively spaced a given distance from the surface ofmicroelectronic workpiece 25 will have an impact on a larger area of themicroelectronic workpiece surface than an anode that is effectivelyspaced from the surface of microelectronic workpiece 25 by a lesseramount. Anodes that are effectively spaced at a comparatively largedistance from the surface of microelectronic workpiece 25 thus have lesslocalized control over the electroplating process than do those that arespaced at a smaller distance. It is therefore desirable to effectivelylocate the anodes in close proximity to the surface of microelectronicworkpiece 25 since this allows more versatile, localized control of theelectroplating process. Advantage can be taken of this increased controlto achieve greater uniformity of the resulting electroplated film. Suchcontrol is exercised, for example, by placing the electroplating powerprovided to the individual anodes under the control of a programmablecontroller or the like. Adjustments to the electroplating power can thusbe made subject to software control based on manual or automated inputs.

In the illustrated embodiment, anode 580 is effectively “seen” bymicroelectronic workpiece 25 as being positioned an approximate distanceA1 from the surface of microelectronic workpiece 25. This is due to thefact that the relationship between the anode 580 and sidewall 560creates a virtual anode having an effective area defined by theinnermost dimensions of sidewall 560. In contrast, anodes 585 areapproximately at effective distances A2, A3, and A4 proceeding from theinnermost anode to the outermost anode, with the outermost anode beingclosest to the microelectronic workpiece 25. All of the anodes 585 arein close proximity (i.e., about 25.4 mm or less, with the outermostanode being spaced from the microelectronic workpiece by about 10 mm) tothe surface of the microelectronic workpiece 25 that is beingelectroplated. Since anodes 585 are in close proximity to the surface ofthe microelectronic workpiece 25, they can be used to provide effective,localized control over the radial film growth at peripheral portions ofthe microelectronic workpiece. Such localized control is particularlydesirable at the peripheral portions of the microelectronic workpiecesince it is those portions that are more likely to have a highuniformity gradient (most often due to the fact that electrical contactis made with the seed layer of the microelectronic workpiece at theoutermost peripheral regions resulting in higher plating rates at theperiphery of the microelectronic workpiece compared to the centralportions thereof).

The electroplating power provided to the foregoing anode arrangement canbe readily controlled to accommodate a wide range of platingrequirements without the need for a corresponding hardware modification.Some reasons for adjusting the electroplating power include changes tothe following:

-   -   seed layer thickness;    -   open area of plating surface (pattern wafers, edge exclusion);    -   final plated thickness;    -   plated film type (copper, platinum, seed layer enhancement);    -   bath conductivity, metal concentration; and    -   plating rate.

The foregoing anode arrangement is particularly well-suited for platingmicroelectronic workpieces having highly resistive seed layers as wellas for plating highly resistive materials on microelectronic workpieces.Generally stated, the more resistive the seed layer or material that isto be deposited, the more the magnitude of the current at the centralanode 580 (or central anodes) should be increased to yield a uniformfilm. This effect can be understood in connection with an example andthe set of corresponding graphs set forth in FIGS. 10 and 11.

FIG. 10 is a graph of four different computer simulations reflecting thechange in growth of an electroplated film versus the radial positionacross the surface of a microelectronic workpiece. The graph illustratesthe changing growth that occurs when the current to a given one of thefour anodes 580, 585 is changed without a corresponding change in thecurrent to the remaining anodes. In this illustration, Anode 1corresponds to anode 580 and the remaining Anodes 2 through 4 correspondto anodes 585 proceeding from the interior most anode to the outermostanode. The peak plating for each anode occurs at a different radialposition. Further, as can be seen from this graph, anode 580, beingeffectively at the largest distance from the surface of the workpiece,has an effect over a substantial radial portion of the workpiece andthus has a broad affect over the surface area of the workpiece. Incontrast, the remaining anodes have substantially more localized effectsat the radial positions corresponding to the peaks of the graph of FIG.10.

The differential radial effectiveness of the anodes 580, 585 can beutilized to provide an effectively uniform electroplated film across thesurface of the microelectronic workpiece. To this end, each of theanodes 580, 585 may be provided with a fixed current that may differfrom the current provided to the remaining anodes. These plating currentdifferences can be provided to compensate for the increased plating thatgenerally occurs at the radial position of the workpiece surfaceproximate the contacts of the cathode contact assembly 85 (FIG. 1B).

The computer simulated effect of a predetermined set of plating currentdifferences on the normalized thickness of the electroplated film as afunction of the radial position on the microelectronic workpiece overtime is shown in FIG. 11. In this simulation, the seed layer was assumedto be uniform at t0. As illustrated. there is a substantial differencein the thickness over the radial position on the microelectronicworkpiece during the initial portion of the electroplating process. Thisis generally characteristic of workpieces having seed layers that arehighly resistive, such as those that are formed from a highly resistivematerial or that are very thin. However, as can be seen from FIG. 11,the differential plating that results from the differential currentprovided to the anodes 580, 585 forms a substantially uniform platedfilm by the end of the electroplating process. It will be recognizedthat the particular currents that are to be provided to anodes 580, 585depends upon numerous factors including, but not necessarily limited to,the desired thickness and material of the electroplated film, thethickness and material of the initial seed layer, the distances betweenanodes 580, 585 and the surface of the microelectronic workpiece,electrolyte bath properties, etc.

Anodes 580, 585 may be consumable, but are preferably inert and formedfrom platinized titanium or some other inert conductive material.However, as noted above, inert anodes tend to evolve gases that canimpair the uniformity of the plated film. To reduce this problem, aswell as to reduce the likelihood of the entry of bubbles into the mainprocessing chamber 505, processing base 37 includes several uniquefeatures. With respect to anode 580, a small fluid flow path forms aVenturi outlet 590 between the underside of anode 580 and the relativelylower pressure channel 540 (see FIG. 2). This results in a Venturieffect that causes the electroplating solution proximate the surfaces ofanode 580 to be drawn away and, further, provides a suction flow (orrecirculation flow) that affects the uniformity of the impinging flow atthe central portion of the surface of the microelectronic workpiece.

The Venturi flow path 590 may be shielded to prevent any large bubblesoriginating from outside the chamber from rising through region 590.Instead, such bubbles enter the bubble-trapping region of theantechamber 510.

Similarly, electroplating solution sweeps across the surfaces of anodes585 in a radial direction toward fluid outlet 572 to remove gas bubblesforming at their surfaces. Further, the radial components of the fluidflow at the surface of the microelectronic workpiece assist in sweepinggas bubbles therefrom.

There are numerous further processing advantages with respect to theillustrated flow through the reactor chamber. As illustrated, the flowthrough the nozzles 535 is directed away from the microelectronicworkpiece surface and, as such, there are no jets of fluid created todisturb the uniformity of the diffusion layer. Although the diffusionlayer may not be perfectly uniform, it will be substantially uniform,and any non-uniformity will be relatively gradual as a result. Further,the effect of any minor non-uniformity may be substantially reduced byrotating the microelectronic workpiece during processing. A furtheradvantage relates to the flow at the bottom of the main chamber 505 thatis produced by the Venturi outlet, which influences the flow at thecenterline thereof. The centerline flow velocity is otherwise difficultto implement and control. However, the strength of the Venturi flowprovides a non-intrusive design variable that may be used to affect thisaspect of the flow.

As is also evident from the foregoing reactor design, the flow that isnormal to the microelectronic workpiece has a slightly greater magnitudenear the center of the microelectronic workpiece and creates adome-shaped meniscus whenever the microelectronic workpiece is notpresent (i.e., before the microelectronic workpiece is lowered into thefluid). The dome-shaped meniscus assists in minimizing bubble entrapmentas the microelectronic workpiece or other workpiece is lowered into theprocessing solution (here, the electroplating solution).

A still further advantage of the foregoing reactor design is that itassists in preventing bubbles that find their way to the chamber inletfrom reaching the microelectronic workpiece. To this end, the flowpattern is such that the solution travels downward just before enteringthe main chamber. As such, bubbles remain in the antechamber and escapethrough holes at the top thereof. Further, the upward sloping inlet path(see FIG. 5 and appertaining description) to the antechamber preventsbubbles from entering the main chamber through the Venturi flow path.

FIGS. 3-5 illustrate a specific construction of a complete processingchamber assembly 610 that has been specifically adapted forelectrochemical processing of a semiconductor microelectronic workpiece.More particularly, the illustrated embodiment is specifically adaptedfor depositing a uniform layer of material on the surface of theworkpiece using electroplating.

As illustrated, the processing base 37 shown in FIG. 1B is comprised ofprocessing chamber assembly 610 along with a corresponding exterior cup605. Processing chamber assembly 610 is disposed within exterior cup 605to allow exterior cup 605 to receive spent processing fluid thatoverflows from the processing chamber assembly 610. A flange 615 extendsabout the assembly 610 for securement with, for example, the frame ofthe corresponding tool.

With particular reference to FIGS. 4 and 5, the flange of the exteriorcup 605 is formed to engage or otherwise accept rotor assembly 75 ofreactor head 30 (shown in FIG. 1B) and allow contact between themicroelectronic workpiece 25 and the processing solution, such aselectroplating solution, in the main fluid flow chamber 505. Theexterior cup 605 also includes a main cylindrical housing 625 into whicha drain cup member 627 is disposed. The drain cup member 627 includes anouter surface having channels 629 that, together with the interior wallof main cylindrical housing 625, form one or more helical flow chambers640 that serve as an outlet for the processing solution. Processingfluid overflowing a weir member 739 at the top of processing cup 35drains through the helical flow chambers 640 and exits an outlet (notillustrated) where it is either disposed of or replenished andre-circulated. This configuration is particularly suitable for systemsthat include fluid re-circulation since it assists in reducing themixing of gases with the processing solution thereby further reducingthe likelihood that gas bubbles will interfere with the uniformity ofthe diffusion layer at the workpiece surface.

In the illustrated embodiment, antechamber 510 is defined by the wallsof a plurality of separate components. More particularly, antechamber510 is defined by the interior walls of drain cup member 627, an anodesupport member 697, the interior and exterior walls of a mid-chambermember 690, and the exterior walls of flow diffuser 525.

FIGS. 3B and 4 illustrate the manner in which the foregoing componentsare brought together to form the reactor. To this end, the mid-chambermember 690 is disposed interior of the drain cup member 627 and includesa plurality of leg supports 692 that sit upon a bottom wall thereof. Theanode support member 697 includes an outer wall that engages a flangethat is disposed about the interior of drain cup member 627. The anodesupport member 697 also includes a channel 705 that sits upon andengages an upper portion of flow diffuser 525, and a further channel 710that sits upon and engages an upper rim of nozzle assembly 530.Mid-chamber member 690 also includes a centrally disposed receptacle 715that is dimensioned to accept the lower portion of nozzle assembly 530.Likewise, an annular channel 725 is disposed radially exterior of theannular receptacle 715 to engage a lower portion of flow diffuser 525.

In the illustrated embodiment, the flow diffuser 525 is formed as asingle piece and includes a plurality of vertically oriented slots 670.Similarly, the nozzle assembly 530 is formed as a single piece andincludes a plurality of horizontally oriented slots that constitute thenozzles 535.

The anode support member 697 includes a plurality of annular groovesthat are dimensioned to accept corresponding annular anode assemblies785. Each anode assembly 785 includes an anode 585 (preferably formedfrom platinized titanium or another inert metal) and a conduit 730extending from a central portion of the anode 585 through which a metalconductor may be disposed to electrically connect the anode 585 of eachassembly 785 to an external source of electrical power. Conduit 730 isshown to extend entirely through the processing chamber assembly 610 andis secured at the bottom thereof by a respective fitting 733. In thismanner, anode assemblies 785 effectively urge the anode Support member697 downward to clamp the flow diffuser 525, nozzle assembly 530,mid-chamber member 690. and drain cup member 627 against the bottomportion 737 of the exterior cup 605. This allows for easy assembly anddisassembly of the processing chamber 610. However, it will berecognized that other means may be used to secure the chamber elementstogether as well as to conduct the necessary electrical power to theanodes.

The illustrated embodiment also includes a weir member 739 thatdetachably snaps or otherwise easily secures to the upper exteriorportion of anode support member 697. As shown, weir member 739 includesa rim 742 that forms a weir over which the processing solution flowsinto the helical flow chamber 640. Weir member 739 also includes atransversely extending flange 744 that extends radially inward and formsan electric field shield over all or portions of one or more of theanodes 585. Since the weir member 739 may be easily removed andreplaced, the processing chamber assembly 610 may be readilyreconfigured and adapted to provide different electric field shapes.Such differing electrical field shapes are particularly useful in thoseinstances in which the reactor must be configured to process more thanone size or shape of a workpiece. Additionally, this allows the reactorto be configured to accommodate workpieces that are of the same size,but have different plating area requirements.

The anode support member 697, with the anodes 585 in place, forms thecontoured sidewall 560 and slanted sidewall 565 that is illustrated inFIG. 2. As noted above, the lower region of anode support member 697 iscontoured to define the upper interior wall of antechamber 510 andpreferably includes one or more gas outlets 665 that are disposedtherethrough to allow gas bubbles to exit from the antechamber 510 tothe exterior environment.

With particular reference to FIG. 5, fluid inlet 515 is defined by aninlet fluid guide, shown generally at 810, that is secured to the floorof mid-chamber member 690 by one or more fasteners 815. Inlet fluidguide 810 includes a plurality of open channels 817 that guide fluidreceived at fluid inlet 515 to an area beneath mid-chamber member 690.Channels 817 of the illustrated embodiment are defined by upwardlyangled walls 819. Processing fluid exiting channels 817 flows therefromto one or more further channels 821 that are likewise defined by wallsthat angle upward.

Central anode 580 includes an electrical connection rod 581 thatproceeds to the exterior of the processing chamber assembly 610 throughcentral apertures formed in nozzle assembly 530, mid-chamber member 690and inlet fluid guide 810. The small Venturi flow path regions shown at590 in FIG. 2 are formed in FIG. 5 by vertical channels 823 that proceedthrough drain cup member 690 and the bottom wall of nozzle member 530.As illustrated, the fluid inlet guide 810 and, specifically, theupwardly angled walls 819 extend radially beyond the shielded verticalchannels 823 so that any bubbles entering the inlet proceed through theupward channels 821 rather than through the vertical channels 823.

FIGS. 6-9 illustrate a further embodiment of an improved reactorchamber. The embodiment illustrated in these figures retains theadvantageous electric field and flow characteristics of the foregoingreactor construction while concurrently being useful for situations inwhich anode/electrode isolation is desirable. Such situations include.but are not limited to, the following:

-   -   instances in which the electrochemical electroplating solution        must pass over an electrode, such as an anode, at a high flow        rate to be optimally effective;    -   instances in which one or more gases evolving from the        electrochemical reactions at the anode surface must be removed        in order to insure uniform electrochemical processing; and    -   instances in which consumable electrodes are used.

With reference to FIGS. 6 and 7, the reactor includes an electrochemicalelectroplating solution flow path into the innermost portion of theprocessing chamber that is very similar to the flow path of theembodiment illustrated in FIG. 2 and as implemented in the embodiment ofthe reactor chamber shown in FIGS. 3A through 5. As such, componentsthat have similar functions are not further identified here for the sakeof simplicity. Rather, only those portions of the reactor thatsignificantly differ from the foregoing embodiment are identified anddescribed below.

A significant distinction between the embodiments exists, however, inconnection with the anode electrodes and the appertaining structures andfluid flow paths. More particularly, the reactor based 37 includes aplurality of ring-shaped anodes 1015, 1020, 1025 and 1030 that areconcentrically disposed with respect to one another in respective anodechamber housings 1017, 1022, 1027 and 1032. As shown, each anode 1015,1020, 1025 and 1030 has a vertically oriented surface area that isgreater than the surface area of the corresponding anodes show in theforegoing embodiments. Four such anodes are employed in the disclosedembodiment, but a larger or smaller number of anodes may be useddepending upon the electrochemical processing parameters and resultsthat are desired. Each anode 1015, 1020, 1025 and 1030 is supported inthe respective anode chamber housing 1017, 1022, 1027 and 1032 by atleast one corresponding support/conductive member 1050 that extendsthrough the bottom of the processing base 37 and terminates at anelectrical connector 1055 for connection to an electrical power source.

In accordance with the disclosed embodiment, fluid flow to and throughthe three outer most chamber housings 1022, 1027 and 1032 is providedfrom an inlet 1060 that is separate from inlet 515, which supplies thefluid flow through an innermost chamber housing 1017. As shown, fluidinlet 1060 provides electroplating solution to a manifold 1065 having aplurality of slots 1070 disposed in its exterior wall. Slots 1070 are influid communication with a plenum 1075 that includes a plurality ofopenings 1080 through which the electroplating solution respectivelyenters the three anode chamber housings 1022, 1027 and 1032. Fluidentering the anode chamber housings 1017, 1022, 1027 and 1032 flows overat least one vertical surface and, preferably, both vertical surfaces ofthe respective anode 1015, 1020, 1025 and 1030.

Each anode chamber housing 1017, 1022, 1027 and 1032 includes an upperoutlet region that opens to a respective cup 1085. Cups 1085, asillustrated, are disposed in the reactor chamber so that they areconcentric with one another. Each cup includes an upper rim 1090 thatterminates at a predetermined height with respect to the other rims,with the rim of each cup terminating at a height that is verticallybelow the immediately adjacent outer concentric cup. Each of the threeinnermost cups further includes a substantially vertical exterior wall1095 and a slanted interior wall 1200. This wall construction creates aflow region 1205 in the interstitial region between concentricallydisposed cups (excepting the innermost cup that has a contoured interiorwall that defines the fluid flow region 1205 and than the outer mostflow region 1205 associated with the outer most anode) that increases inarea as the fluid flows upward toward the surface of the microelectronicworkpiece under process. The increase in area effectively reduces thefluid flow velocity along the vertical fluid flow path, with thevelocity being greater at a lower portion of the flow region 1205 whencompared to the velocity of the fluid flow at the upper portion of theparticular flow region.

The interstitial region between the rims of concentrically adjacent cupseffectively defines the size and shape of each of a plurality of virtualanodes, each virtual anode being respectively associated with acorresponding anode disposed in its respective anode chamber housing.The size and shape of each virtual anode that is seen by themicroelectronic workpiece under process is generally independent of thesize and shape of the corresponding actual anode. As such, consumableanodes that vary in size and shape over time as they are used can beemployed for anodes 1015, 1020, 1025 and 1030 without a correspondingchange in the overall anode configuration is seen by the microelectronicworkpiece under process. Further, given the deceleration experienced bythe fluid flow as it proceeds vertically through flow regions 1205, ahigh fluid flow velocity may be introduced across the vertical surfacesof the anodes 1015, 1020, 1025 and 1030 in the anode chamber housings1022, 1027 and 1032 while concurrently producing a very uniform fluidflow pattern radially across the surface of the microelectronicworkpiece under process. Such a high fluid flow velocity across thevertical surfaces of the anodes 1015, 1020, 1025 and 1030, as notedabove, is desirable when using certain electrochemical electroplatingsolutions, such as electroplating fluids available from Atotech.Further, such high fluid flow velocities may be used to assist inremoving some of the gas bubbles that form at the surface of the anodes,particularly inert anodes. To this end, each of the anode chamberhousings 1017, 1022, 1027 and 1032 may be provided with one or more gasoutlets (not illustrated) at the upper portion thereof to vent suchgases.

Of further note, unlike the foregoing embodiment, element 1210 is asecurement that is formed from a dielectric material. The securement1210 is used to clamp a plurality of the structures forming reactor base37 together. Although securement 1210 may be formed from a conductivematerial so that it may function as an anode, the innermost anode seenby the microelectronic workpiece under process is preferably a virtualanode corresponding to the interior most anode 1015.

FIGS. 8 and 9 illustrate computer simulations of fluid flow velocitycontours of a reactor constructed in accordance with the embodimentshown in FIGS. 10 through 12. In this embodiment, all of the anodes ofthe reactor base may be isolated from a flow of fluid through the anodechamber housings. To this end, FIG. 8 illustrates the fluid flowvelocity contours that occur when a flow of electroplating solution isprovided through each of the anode chamber housings, while FIG. 9illustrates the fluid flow velocity contours that occur when there is noflow of electroplating solution provided through the anode chamberhousings past the anodes. This latter condition can be accomplished inthe reactor of by turning off the flow the flow from the second fluidflow inlet (described below) and may likewise be accomplished in thereactor of FIGS. 6 and 7 by turning of the fluid flow through inlet1060. Such a condition may be desirable in those instances in which aflow of electroplating solution across the surface of the anodes isfound to significantly reduce the organic additive concentration of thesolution.

FIG. 12 illustrates a variation of the reactor embodiment shown in FIG.7. For the sake of simplicity, only the elements pertinent to thefollowing discussion are provided with reference numerals.

This further embodiment employs a different structure for providingfluid flow to the anodes 1015, 1020, 1025 and 1030. More particularly,the further embodiment employs an inlet member 2010 that serves as aninlet for the supply and distribution of the processing fluid to theanode chamber housings 1017, 1022, 1027 and 1032.

With reference to FIGS. 12 and 13, the inlet member 2010 includes ahollow stem 2015 that may be used to provide a flow of electroplatingfluid. The hollow stem 2015 terminates at a stepped hub 2020. Steppedhub 2020 includes a plurality of steps 2025 that each include a groovedimensioned to receive and support a corresponding wall of the anodechamber housings. Processing fluid is directed into the anode chamberhousings through a plurality of channels 2030 that proceed from amanifold area into the respective anode chamber housing.

This latter inlet arrangement assists in further electrically isolatinganodes 1015, 1020, 1025 and 1030 from one another. Such electricalisolation occurs due to the increased resistance of the electrical flowpath between the anodes. The increased resistance is a direct result ofthe increased length of the fluid flow paths that exist between theanode chamber housings.

The manner in which the electroplating power is supplied to themicroelectronic workpiece at the peripheral edge thereof effects theoverall film quality of the deposited metal. Some of the more desirablecharacteristics of a contact assembly used to provide suchelectroplating power include, for example, the following:

-   -   uniform distribution of electroplating power about the periphery        of the microelectronic workpiece to maximize the uniformity of        the deposited film;    -   consistent contact characteristics to insure wafer-to-wafer        uniformity;    -   minimal intrusion of the contact assembly on the microelectronic        workpiece periphery to maximize the available area for device        production; and    -   minimal plating on the barrier layer about the microelectronic        workpiece periphery to inhibit peeling and/or flaking.

To meet one or more of the foregoing characteristics, reactor assembly20 preferably employs a contact assembly 85 that provides either acontinuous electrical contact or a high number of discrete electricalcontacts with the microelectronic workpiece 25. By providing a morecontinuous contact with the outer peripheral edges of themicroelectronic workpiece 25, in this case around the outercircumference of the semiconductor wafer, a more uniform current issupplied to the microelectronic workpiece 25 that promotes more uniformcurrent densities. The more uniform current densities enhance uniformityin the depth of the deposited material.

Contact assembly 85, in accordance with a preferred embodiment, includescontact members that provide minimal intrusion about the microelectronicworkpiece periphery while concurrently providing consistent contact withthe seed layer. Contact with the seed layer is enhanced by using acontact member structure that provides a wiping action against the seedlayer as the microelectronic workpiece is brought into engagement withthe contact assembly. This wiping action assists in removing any oxidesat the seed layer surface thereby enhancing the electrical contactbetween the contact structure and the seed layer. As a result,uniformity of the current densities about the microelectronic workpieceperiphery arc increased and the resulting film is more uniform. Further,such consistency in the electrical contact facilitates greaterconsistency in the electroplating process from wafer-to-wafer therebyincreasing wafer-to-wafer uniformity.

Contact assembly 85, as will be set forth in further detail below, alsopreferably includes one or more structures that provide a barrier,individually or in cooperation with other structures, that separates thecontact/contacts, the peripheral edge portions and backside of themicroelectronic workpiece 25 from the plating solution. This preventsthe plating of metal onto the individual contacts and, further, assistsin preventing any exposed portions of the barrier layer near the edge ofthe microelectronic workpiece 25 from being exposed to theelectroplating environment. As a result, plating of the barrier layerand the appertaining potential for contamination due to flaking of anyloosely adhered electroplated material is substantially limited.Exemplary contact assemblies suitable for use in the present system areillustrated in U.S. Ser. No. 09/113,723, while Jul. 10, 1998, entitled“PLATING APPARATUS WITH PLATING CONTACT WITH PERIPHERAL SEAL MEMBER”,which is hereby incorporated by reference.

One or more of the foregoing reactor assemblies may be readilyintegrated in a processing tool that is capable of executing a pluralityof processes on a workpiece, such as a semiconductor microelectronicworkpiece. One such processing tool is the LT-210™ electroplatingapparatus available from Semitool, Inc., of Kalispell, Mont. FIGS. 14and 15 illustrate such integration.

The system of FIG. 14 includes a plurality of processing stations 1610.Preferably, these processing stations include one or more rinsing/dryingstations and one or more electroplating stations (including one or moreelectroplating reactors such as the one above), although furtherimmersion-chemical processing stations constructed in accordance withthe of the present invention may also be employed. The system alsopreferably includes a thermal processing station, such as at 1615, thatincludes at least one thermal reactor that is adapted for rapid thermalprocessing (RTP).

The workpieces are transferred between the processing stations 1610 andthe RTP station 1615 using one or more robotic transfer mechanisms 1620that are disposed for linear movement along a central track 1625. One ormore of the stations 1610 may also incorporate structures that areadapted for executing an in-situ rinse. Preferably, all of theprocessing stations as well as the robotic transfer mechanisms aredisposed in a cabinet that is provided with filtered air at a positivepressure to thereby limit airborne contaminants that may reduce theeffectiveness of the microelectronic workpiece processing.

FIG. 15 illustrates a further embodiment of a processing tool in whichan RTP station 1635, located in portion 1630, that includes at least onethermal reactor, may be integrated in a tool set. Unlike the embodimentof FIG. 14, in this embodiment, at least one thermal reactor is servicedby a dedicated robotic mechanism 1640. The dedicated robotic mechanism1640 accepts workpieces that are transferred to it by the robotictransfer mechanisms 1620. Transfer may take place through anintermediate staging door/area 1645. As such, it becomes possible tohygienically separate the RTP portion 1630 of the processing tool fromother portions of the tool. Additionally, using such a construction, theillustrated annealing station may be implemented as a separate modulethat is attached to upgrade an existing tool set. It will be recognizedthat other types of processing stations may be located in portion 1630in addition to or instead of RTP station 1635.

Numerous modifications may be made to the foregoing system withoutdeparting from the basic teachings thereof. Although the presentinvention has been described in substantial detail with reference to oneor more specific embodiments, those of skill in the art will recognizethat changes may be made thereto without departing from the scope andspirit of the invention as set forth herein.

1-22. (canceled)
 23. An apparatus for electrochemical processing ofmicroelectronic workpieces, comprising: a head assembly having aworkpiece holder including a contact assembly with a plurality ofelectrical contacts configured to engage a perimeter portion of aworkpiece; a processing chamber having a weir at a first elevationconfigured to define a surface level of electrochemical processingsolution under the workpiece holder; a first electrode in the processingchamber, a second electrode in the processing chamber concentric withthe first electrode, and a dielectric separator between the first andsecond electrodes, wherein the dielectric separator is at a secondelevation below the first elevation; and an overflow collector externalto the processing chamber to receive processing solution overflowing theweir.
 24. The apparatus of claim 23 wherein the first electrodecomprises a first annular conductive member and the second electrodecomprises a second annular conductive member.
 25. The apparatus of claim24 wherein the first annular conductive member comprises a firstconductive ring and the second annular conductive member comprises asecond conductive ring.
 26. The apparatus of claim 23, furthercomprising a field shield between the workpiece holder and at least oneof the electrodes configured to shield at least a portion of theworkpiece from at least a portion of one of the electrodes.
 27. Theapparatus of claim 26 wherein the field shield comprises an annulusaligned with a peripheral portion of the workpiece holder.
 28. Theapparatus of claim 26 wherein the field shield comprises a flangeextending transversely with respect to the central axis.
 29. Theapparatus of claim 26 wherein the field shield comprises a horizontalflange extending radially inward over a portion of the outer electrode.30. The apparatus of claim 23 wherein the processing chamber furthercomprises a plurality of electrode chamber housings below the weir, theelectrode chamber housings including a first electrode chamber housingcontaining the first electrode and a second electrode chamber housingcontaining the second electrode, wherein the second electrode chamberhousing is concentric with the first electrode chamber housing.
 31. Theapparatus of claim 30 wherein the first electrode chamber housing isseparated from the second electrode chamber housing by an annular wall.32. The apparatus of claim 31 wherein the first electrode comprises afirst annular conductive member and the second electrode comprises asecond annular conductive member.
 33. The apparatus of claim 32 whereinthe first annular conductive member comprises a first conductive ringand the second annular conductive member comprises a second conductivering.
 34. The apparatus of claim 30 further comprising a first lateraldielectric member above the first electrode and a second dielectricmember above the second electrode.
 35. The apparatus of claim 23,further comprising a controller operatively coupled to the electrodes,wherein the controller is programmed to apply a first current to thefirst conductive member and a second current different than the firstcurrent to the second conductive member.
 36. An apparatus forelectrochemical processing of microelectronic workpieces, comprising: aworkpiece holder having a support member with an opening configured toreceive a workpiece and a plurality of flexible conductive contactsprojecting into the opening, the contacts having conductive contactportions arranged to contact a perimeter portion of the workpiece; aprocessing chamber including a weir at a first elevation, a plurality ofelectrode compartments at one or more elevations below the firstelevation, and a flow distributor configured to deliver processingsolution to at least one electrode compartment; a first electrode in thefirst electrode compartment and a second electrode in the secondelectrode compartment surrounding the first electrode; and an overflowcollector external to the processing chamber to receive processingsolution overflowing the weir.
 37. The apparatus of claim 36 wherein thefirst electrode comprises a first annular conductive member and thesecond electrode comprises a second annular conductive member.
 38. Theapparatus of claim 37 wherein the first annular conductive membercomprises a first conductive ring and the second annular conductivemember comprises a second conductive ring.
 39. The apparatus of claim36, further comprising a field shield between the workpiece holder andat least one of the electrodes configured to shield at least a portionof the workpiece from at least a portion of one of the electrodes. 40.The apparatus of claim 39 wherein the field shield comprises an annulusaligned with a peripheral portion of the workpiece holder.
 41. Theapparatus of claim 39 wherein the field shield comprises a flangeextending transversely with respect to the central axis.
 42. Theapparatus of claim 39 wherein the field shield comprises a horizontalflange extending radially inward over a portion of the outer electrode.43. The apparatus of claim 36 wherein the first electrode compartmentcomprises a first electrode chamber housing containing the firstelectrode and the second electrode compartment comprises a secondelectrode chamber housing containing the second electrode, wherein thesecond electrode chamber housing is concentric with the first electrodechamber housing.
 44. The apparatus of claim 43 wherein the firstelectrode chamber housing is separated from the second electrode chamberhousing by an annular wall.
 45. The apparatus of claim 44 wherein thefirst electrode comprises a first annular conductive member and thesecond electrode comprises a second annular conductive member.
 46. Theapparatus of claim 45 wherein the first annular conductive membercomprises a first conductive ring and the second annular conductivemember comprises a second conductive ring.
 47. The apparatus of claim 43further comprising a first lateral dielectric member above the firstelectrode and a second dielectric member above the second electrode. 48.The apparatus of claim 36, further comprising a controller operativelycoupled to the electrodes, wherein the controller is programmed to applya first current to the first conductive member and a second currentdifferent than the first current to the second conductive member.
 49. Anapparatus for electrochemical processing of microelectronic workpieces,comprising: a head assembly having a workpiece holder including acontact assembly with a plurality of electrical contacts configured toengage a perimeter portion of. a workpiece; a processing chamber havinga inner vessel, an annular dielectric divider in the inner vessel at oneelevation, and a weir at another elevation above the elevation of thedielectric divider; a plurality of electrodes in the inner vessel, theplurality of electrodes including a first electrode being an innermostelectrode relative to a central axis of the processing chamber and asecond electrode surrounding the first electrode; and an externaloverflow collector around the processing chamber.
 50. An tool forelectrochemical processing of microelectronic workpieces, comprising: acabinet having a plurality of processing stations; a robotic transfermechanism for transferring microelectronic workpieces relative to theprocessing stations; an electrochemical processing apparatus at aprocessing station, the electrochemical processing apparatus having ahead assembly, a processing chamber having a weir at a first elevationand an annular dielectric divider at a second elevation below the firstelevation, a plurality of independently operable electrodes in theprocessing chamber including a first electrode on one side of thedivider and a second electrode on another side of the divider, and anoverflow collector external to the processing chamber, the head assemblyhaving a workpiece holder configured to carry a workpiece and a contactassembly including a plurality of contacts arranged to contact aperimeter portion of the workpiece, and the overflow collector beingconfigured to receive processing solution overflowing the weir.
 51. Amethod for processing a microelectronic workpiece in a processingstation having an exterior cup, a processing chamber in the exteriorcup, a first electrode in the processing chamber, and a second electrodein the processing chamber arranged concentrically with the firstelectrode, comprising: directing a flow of processing solution throughthe processing chamber; providing an electrical current to the workpiecevia a plurality of electrical contacts engaging a perimeter portion ofthe workpiece; applying a first electrical bias to the first electrode;applying a second electrical bias to the second electrode; and flowingthe processing solution over a weir of the processing chamber and intoan external overflow collector.
 52. The method of claim 51 wherein thefirst electrical bias applied to the first electrode is different thanthe second electrical bias applied to the second electrode.
 53. Anapparatus for electrochemically processing microelectronic workpieces,comprising: a workpiece holder including contact means for electricallybiasing a workpiece and for holding the workpiece at a processingregion; means for directing a uniform electrolyte flow upwardly towardthe workpiece holder to crest at the processing region, the directingmeans being in a processing chamber; means for biasing the electrolyteflow differentially relative to a radial position within the processingchamber, wherein the biasing means includes first and secondelectrically conductive electrodes in the processing chamber; andoverflow means for receiving the electrolyte flow downstream from theprocessing region, wherein the processing chamber is a separate vesselrelative to the overflow means.
 54. The apparatus of claim 53 whereinthe overflow means comprises an exterior cup containing the processingchamber.